In this photo, pink coral is seen on the Palmyra Atoll in the Pacific. Parts of three remote and uninhabited Pacific island chains were set aside by President George W. Bush as national monuments to protect them from oil and gas extraction and commercial fishing.

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Efforts to set aside conservation zones in the world's oceans are picking up steam, putting countries on a path to reach an international goal of setting aside 10 percent of coastal and marine waters as marine-protected areas by 2020.

Marine-protected areas, or MPAs, generally are designed as free-swim zones for a wide range of ocean life, giving them havens to reproduce and grow without pressure from fishing or other ecologically disruptive human activities.

The ultimate goal is to ensure that the world's oceans maintain a healthy level of biological diversity even as they continue to serve the needs of millions of people who either make their living from fishing or rely on the sea as a main source of food.

In raw numbers, the extent of protected areas is small compared with available square miles of ocean, acknowledges Mark Spalding, senior marine scientist at the Nature Conservancy who led the team that pulled the data together. Indeed, MPAs currently cover far less than 1 percent of the world's oceans.

But the pace at which reserves are growing is picking up.

Between 2003 and 2007, MPAs grew at a rate of about 11.8 percent a year to cover about 2.5 million square kilometers (about 965,000 square miles). By 2010, MPAs covered about 4.8 million square kilometers, an average growth rate of 31 percent for each of the intervening three years. This year, MPAs cover about 8.2 million square kilometers, which would put the growth rate since 2010 at an average of 35 percent a year.

Over the next 12 to 24 months, another 5.2 million square kilometers could be added if the Cook Islands, Australia, and New Caledonia follow through on their plans to establish or expand protected areas.

Protected areas are being added so fast that "you can't keep up to date with these things," Dr. Spalding says. "It's a huge acceleration."

One reason the growth rate has picked up: A few countries have been picking the low-hanging fruit. They are preserving vast expanses of pristine marine ecosystems that are off the beaten nautical path.

Environmentalists hailed that move in no small part because keeping reefs in these areas as untouched as possible leaves them to serve as reference points for ecologists as they strive to restore stressed reefs elsewhere in the tropics. But the remoteness also meant that setting these areas aside presented relatively low opportunity costs politically compared with similar efforts along continental coasts.

Originally, nations had agreed to meeting the 10 percent coverage target by 2012. But by 2010, it was obvious that wasn't going to happen, Spalding explains. At a UN biodiversity conference that year in Nagoya, Japan, negotiators extended the deadline to 2020. But they also reworded the goals in ways aimed to provide more-specific direction on what was to be protected.

For instance, no longer was it enough merely to add patches of ocean anywhere. MPAs were to include regions that humans rely on for food or economic benefits, as well as regions that safeguard biodiversity. The new goals also noted that conservation efforts needed to reach deep inland to include areas whose runoff flows into the rivers that empty into coastal waters.

These represent the high-hanging fruit. These goals are difficult to achieve politically and so require close cooperation among all parties interested in using marine resources, ranging from fish underwater to offshore wind farms that seek to exploit ocean winds.

Some countries are moving in this direction, although generally the steps remain small, Spalding says. But word on the benefits of MPAs is getting around – from regional pacts, such as one signed in 2007 for a vast expanse of the western Pacific known as the Coral Triangle, to fisher-to-fisher exchanges in which those from well-managed marine areas share their experiences with those from poorly managed areas.

Referring to a well-designed MPA – one that brings benefits to the livelihoods of all the potential stakeholders – Spalding says: "If you get it right, you'll be generating such benefits for people that the whole system should snowball. People look over their shoulders, see an MPA down the road, and say: 'We want one of those.' "